How to Identify Diamond Trevally

To identify Diamond Trevally (Alectis indicus), look at these key features.

Physical Characteristics

Body shape

compressed

Coloration

Adults are silvery-blue to silvery-green dorsally, fading to silvery-white ventrally. Juveniles often have several faint, broad, dark vertical bands on their sides, which fade with age. The fins are typically dusky to hyaline.

Scale type

cycloid

Mouth position

terminal

Distinctive features

Highly compressed, deep body, especially in juveniles., Extremely long, filamentous dorsal and anal fin rays in juveniles, which can be several times the body length., Steeply rising head profile., Lateral line with a strong arch anteriorly, becoming straight posteriorly, with a moderate number of scutes (20-30) on the straight part., Small, embedded scales, giving a smooth appearance.

Dorsal fin

Two dorsal fins; the first with 7-8 spines (often embedded in adults), the second with 1 spine and 18-20 soft rays. The anterior soft rays of the second dorsal fin are greatly elongated in juveniles.

Tail fin

Deeply forked caudal fin.

Pectoral fin

Long, falcate pectoral fins.

Distinctive fins

Anal fin with 2 detached spines followed by 1 spine and 15-17 soft rays. Anterior soft rays of the anal fin are also greatly elongated in juveniles.

Identification Tips

1. 1

   Body Shape and Filaments

   Juveniles are unmistakable due to their extremely deep, compressed body and exceptionally long, trailing dorsal and anal fin filaments. Adults retain the deep, compressed body but lose the extreme filament length.

2. 2

   Head Profile

   The steeply rising, almost vertical head profile is a key characteristic, especially in adults.

3. 3

   Scutes

   Count the scutes on the straight part of the lateral line (20-30) to differentiate from other Carangids.

4. 4

   Coloration

   Silvery body with faint vertical bands in juveniles, fading to uniform silvery in adults.

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